Assessment of Geant4 Prompt-Gamma Emission Yields in the Context of Proton Therapy Monitoring

International audienceMonte Carlo tools have been long used to assist the research and development of solutions for proton therapy monitoring. The present work focuses on the prompt-gamma emission yields by comparing experimental data with the outcomes of the current version of Geant4 using all applicable proton inelastic models. For the case in study and using the binary cascade model, it was found that Geant4 overestimates the prompt-gamma emission yields by 40.2 ± 0.3%, even though it predicts the prompt-gamma profile length of the experimental profile accurately. In addition, the default implementations of all proton inelastic models show an overestimation in the number of prompt gammas emitted. Finally, a set of built-in options and physically sound Geant4 source code changes have been tested in order to try to improve the discrepancy observed. A satisfactory agreement was found when using the QMD model with a wave packet width equal to 1.3 fm 2

Real-Time Online Monitoring of the Ion Range by Means of Prompt Secondary Radiations

International audiencePrompt secondary radiations such as gamma rays and protons can be used for ion-range monitoring during ion therapy either on an energy-slice basis or on a pencil-beam basis. We present a review of the ongoing activities in terms of detector developments, imaging, experimental and theoretical physics issues concerning the correlation between the physical dose and hadronic processe

Contribution à l'imagerie et à la dosimétrie des rayonnements ionisants : traitement du signal et simulation en physique de transport de particules

Françoise Peyrin, rapporteure ; Frédéric Truchetet, rapporteur ; Albert Heinrich Walenta, rapporteur ; Daniel Babot ; Rolf Clackdoyle ; Denis Dauvergne ; Ali Mohammad-Djafar

Region-of-Interest CT Reconstruction using One-Endpoint Hilbert Inversion in Optimized Directions

International audienceIn computed tomography, scanning the entire object is sometimes impossible, causing truncated projection data. Reconstruction is however still possible: using differentiated backprojection, the Hilbert transform of the object can be calculated and inverted along line segments in the field-of-view. When two endpoints of the line segment are outside the object extent, a stable analytic reconstruction formula exists. When only one endpoint is outside the object extent, every pixel can be reconstructed, but no inversion formula is known yet. Uniqueness of the inverse Hilbert transform is nevertheless guaranteed along such segments, and a numerical inverse can be used. Most pixels of the field-of-view accept more than one "one-endpoint line segment" and one can choose the direction; we propose here to select the optimal direction based on an empirical criterion. Image quality improvement is assessed against a reconstruction that uses a single direction for every pixel

Stereokinematic analysis of visual data in active convergent stereoscopy

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Movement detection process in monocular imaging with fixed acquisition system.

EP Patent 0,587,469International audienc

Le contrôle par radiographie

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Characterization of internal fatigue cracks in aluminum alloys by simulation of phase contrast tomography

International audienceSynchrotron Radiation Computed Tomography (SRCT) allows a better detection of fatigue cracks in metals than laboratory CT due to the existence of phase contrast. However the presence in reconstructed images of fringes at the edges of objects generated by Fresnel diffraction makes it difficult to identify and analyze the cracks quantitatively. Simulations of phase contrast synchrotron tomography images containing cracks with different sizes and shapes are obtained by using GATE software. Analyzing the simulation results, firstly, we confirmed that the bright parts with strong contrast in SRCT image are streak artifacts; secondly, we found that the gray scale values within the cracks in SRCT images are related to the crack size; these simulation results are used to analyse SRCT images of internal fatigue cracks in a cast Al alloy, providing a clearer visualisation of damage